update UPGRADING.md with breaking changes

Author: umbynos

docs/UPGRADING.md

@@ -2,6 +2,22 @@
 
 Here you can find a list of migration guides to handle breaking changes between releases of the CLI.
 
+## Unreleased
+### `board details` arguments change
+
+The `board details` command now accept only the `-b` flag to specify the fqbn.
+
+`board details <fqbn>` has been deprecated in favour of `board details -b <fqbn>`.
+
+### `board attach` arguments change
+
+The `board attach` command now accept `-p` and `-b` flags to respectively select the board fqbn and the port.
+
+`board attach [<port|fqbn>] <sketch-path> has been deprecated in favour of`board attach [-b <fqbn> | -p <port>]f <sketh-path>`.
+
+### `--timeout` flag in `board list` command have been replaced by `--discovery-timeout`
+
+The flag `--timeout` in the `board list` command has been deprecated in favour of `--discovery-timeout`.
 ## 0.19.0
 
 ### `board list` command JSON output change